Brexit Secretary David Davis will launch a first round of negotiations on Britain's withdrawal from the European Union on Monday when he meets the EU's Michel Barnier for four days of talks between their teams in Brussels.

A month after a first meeting, the EU’s Brexit negotiator will press Davis to agree to Britain covering substantial British financial commitments and offer more detail on other British proposals.

Davis said his priority was to "lift the uncertainty" for EU citizens living in the UK and Britons living in the EU.

The EU says there must be substantial progress on this - and on a financial settlement and the issue of the Irish border - before trade talks can begin.

With just 20 months to settle divorce terms before Britain leaves, deal or no deal, on March 30, 2019, the 27 other EU national leaders want British Prime Minister Theresa May to rally her divided nation swiftly behind a clear, detailed plan that can minimise economic and social disruption across Europe as its second biggest economy cuts loose from the continent.

Negotiators will break into groups discussing four key areas of priorities before a planned news conference on Thursday.

Working groups will focus on three areas: citizens' rights; the EU demand that Britain pays some €60 billion to cover ongoing EU budget commitments; and other loose ends, such as what happens to British goods in EU shops on Brexit Day.

A fourth set of talks, run by Davis and Barnier's deputies Oliver Robbins and Sabine Weyand, will focus on curbing problems in Northern Ireland once a new EU land border separates the British province from EU member Ireland to the south. Some of that will have to wait for clarity on future trade relations.

Davis and Barnier will shake hands for the cameras at the European Commission's Berlaymont headquarters at 8:15am before a first full session of talks.

"We made a good start last month, and this week we’ll be getting into the real substance," Davis said in remarks prepared for delivery ahead of the meeting.

His office described an offer made by Britain last month as "fair and serious", though Barnier has dismissed it as falling short of the EU demand that its 3 million citizens in Britain keep all their existing rights for life and have recourse to the EU courts to enforce those rights even after Britain has left.